Logic 7 & earlier Must move from v7.2 to X: what will I lose?

After seven years of happily using my Logic Pro version 7.2 (on an older Intel Mac Pro tower), the XSKey seems to have died and even after re-install, it still does not read the dongle's serial number to let me "in" to the program. I really don't mind spending the $200 to move up to Logic X on my new iMac and I'm sure I will love the new features, but I'm worried that there has been so much time and changes to the program that my old projects may not work right. What should I generally expect? Does version X still have all my same synths and EXS24sampler and the various samples I got with the original v.7? Will X even open my old projects??

I'll be doing some more research, but this caught me by surprise today and I'm a bit worried that I'll be starting from total scratch in a new environment and will lose all my hard-won sound presets, etc, just because I can't start up the old program.